Question

I have an array with numerous dimensions, and I want to test for the existence of a cell.

The below cascaded approach, will be for sure a safe way to do it:

if (array_key_exists($arr, 'dim1Key'))  
  if (array_key_exists($arr['dim1Key'], 'dim2Key'))  
    if (array_key_exists($arr['dim1Key']['dim2Key'], 'dim3Key'))  
      echo "cell exists";  

But is there a simpler way?

I’ll go into more details about this:

1. Can I perform this check in one single statement?
2. Do I have to use array_key_exist or can I use something like isset? When do I use each and why?

Answer 1

isset() is the cannonical method of testing, even for multidimensional arrays. Unless you need to know exactly which dimension is missing, then something like

isset($arr[1][2][3])

is perfectly acceptable, even if the [1] and [2] elements aren’t there (3 can’t exist unless 1 and 2 are there).

However, if you have

$arr['a'] = null;

then

isset($arr['a']); // false
array_key_exists('a', $arr); // true

comment followup:

Maybe this analogy will help. Think of a PHP variable (an actual variable, an array element, etc…) as a cardboard box:

• isset() looks inside the box and figures out if the box’s contents can be typecast to something that’s “not null”. It doesn’t care if the box exists or not – it only cares about the box’s contents. If the box doesn’t exist, then it obviously can’t contain anything.
• array_key_exists() checks if the box itself exists or not. The contents of the box are irrelevant, it’s checking for traces of cardboard.